Excellent Dresden Lakes Cyclopteris Plant Fossil

Description: The Mazon Creek deposits of the region near Braidwood, Illinois rival the other famous Lagerstatten of the Burgess Shale, Solnhofen, and Liaoning for the variety of detailed life preserved. Many exquisitely-preserved specimens are found in the ironstone nodules that make up the deposits. The majority of collecting areas are the spoil heaps of abandoned coal mines. This particular nodule, however, comes from Dresden Lakes in Grundy County Illinois. Like the better-known Pit 11 site near Braidwood, Illinois, this location became the site for cooling ponds for a nuclear power plant. The site is well known for the dark coloration that while esthetically pleasing is somewhat harder to photograph. I recently had an opportunity to acquire a collection that was made in the 1950’s. Pteridosperms or seed ferns are a group of extinct plants with mostly fern-like foliage but with real seeds. They are mostly reconstructed as small trees but also forms with a climbing growth habit gave been found. Some forms, notably those called the Medullosales, have large fronds which could be up several meters long. Several groups can be distinguished within the Pteridosperms. The Pteridosperms evolved in the latest Devonian, and became common in the Carboniferous. The Medullosales took over the leading role during the Westphalian and persisted into the Permian. This one is known as Cyclopteris, a term reserved for these distinctive isolated pinnules. All the cyclopterids are most likely members of the genus Neuropteris (see my other offerings), but the parent plant has not yet been identified. This fine example completely fills its enclosing nodule.